Bushings have been used to protect electrical cables in various applications such as passage through bulkheads, firewalls, panels, etc. With the increased use of metal studs for framing buildings, electrical cables must be passed through holes within metal studs. In the past framing studs were commonly constructed of wood, and cables passed through holes or openings in wood studs were not abraded by the relatively soft sides of the opening. Today, it is becoming common to frame a commercial building or residential house with metal studs. Openings in the metal studs, either pre-stamped or pre-cut or those drilled or punched at the construction site, commonly have sharp edges that can easily catch and abrade the insulating layer of an electrical cable. Cables must be protected when they are pulled through openings in metal studs.
It is common to protect electrical cables from abrasion with openings by installing a bushing that matches the contours of the opening. A major disadvantage to this approach occurs when the opening is of an irregular shape, requiring the installer to stock a variety of different shaped bushings.
It has also been common to provide bushings that consist of two parts, or one part with two sections hinged together. The parts or sections of the bushing are snapped together through the opening to create a non-abrasive edge for protecting cables.